Telephone system



2 Sheets-Sheet 1.

(No Model.)

A. E. DOLBEAB.

TELEPHONE SYSTEM. 7 No. 325,659. Patented Sept. 8, 1885.

H1 IIIIHIII jlh esses. T ie MWVQWZM UNITED STATES AMOS EMERSON DQLBEAR, OF BOSTON, MASSACHUSETTS.

TELEPHONE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 325,659, dated September 8, 1885. Application tiled April 15, 1883. (No model.)

To all whom it may concern:

Be it known that I, Amos Errnnson DoL- BEAR, of Boston, (Somerville,) in the county of -Middlesex and State of Massachusetts, have invented certain Improvements in Telephone Systems, of which the following is a specification, reference being had to the accompanying drawings, forming a part hereof.

My invention relates to that class of telephones described in my Patents No. 239,742, dated April 5, 1881, and No. 240,578, dated ApriliZG, 1881.

In the drawings, Figure 1 is a front elevation, and Fig. 2 a side elevation, of the apparatus used at each station. Figs. 3 and 4. are diagrams to show more clearly the arrangements of circuits new with me.

The apparatus, as shown in the drawings, consists of the transmitter T, receiver R, induction-coil I, battery 13, signaling mechanism S, primary circuit a a, 850., line or secondary circuit Z Z, &c., and signal-circuit s s, &c., which, of course, forms part of the line or secondary circuit when in use. These circuits should be provided with proper switches, by which the transmitter may be out out of the primary circuit when that circuit is used for charging the receiver-plates or for signaling, and the signaling mechanism be cut out of the line when conversation is carried on, and the primary circuit must be provided with a proper circuit-closer, by which the primary circuit is made and broken, in order to induce currents in the line, and thereby operate the signaling mechanism, (and charge the receivers when my receivers are used.)

In practiceall the receivers It are on their hooks 0' until a station (say station 1) is called, and as long as the receiver R of station 1 is on its book a the rod (1, carried by hook r, is in contact with the two springs f f, and consequently the line is closed from binding-post Z, by which the line connects with the apparatus on one side, through signaling mechanism S to bindingpost Z, by which the line connects with the apparatus on the other side, the circuit extending through wire 8, key 7c is, wire 8', switch f (lf, wire s", and wire 5'; and as line Z is grounded at each end, there is a complete circuit from the secondary coil of each station through the signaling mechanism of all the other stations on the line. At the calling-station-say station 2 of Fig. 3-the caller presses upon the knob of key It, and thereby forces k into contact with 70 and k, which breaks contact between 7t and k, (for the purpose of throwing out his own signaling mechanism S.) He then operates circuit-closer g h, making and breaking the primary circuit B, a g h, w, k W, a, and (6, thereby inducing currents in the line Z, which actuate the signaling mechanism S at station 1, (and all others in the line,) as before described. After station 1 has been called and answered, the receivers are taken from their hooks, which closes switch f d f, and also closes switch f* f in the primary circuit. The primary is then through E a a f a To? h 9 a and the secondary circuit 1 is complete from G through ll Z l 2 f (if Z Z Z through all the stations on the line to G.

In case there be only two stations in the line, as in Fig. 3, both receivers will of course conversation. That example of my invention illustrated in the drawings is therefore limited, practically, to private lines, for all the stations must be called to call any of them, and each must take its receiver off its hook to learn which is wanted. In case of a large number of stations on one line, especial circuit-breakers will be used at each station and provision made for individual calls. In this case, if station 3 call station 1.,I ig. 4, the line for conversation between 3 and 1 will be through 5 k k sf df s S s of station 2 and of all other stations not called.

This invention relates to the utilization in telephone-lines of the primary circuit and its battery for calling, and to a special arrangement of my receiver with a closed circuit; and these features can be better shown in the arrangement for private lines than in the more complicated arrangements where a central office is used or where individual calls-that is, especial circuit-brcakersare in the primary of each station; hence it is deemed unnecessary to describe here the details of those more complicated arrangements.

Of course, if magnetoreceivers be used,they must be in the complete circuit above described. For example, as shown by the dotted lines m m m m mflwhere that part of the line marked Z is supposed to extend by line or to be ofi their hooks when the line is in use form, thence through the magneto-receiver m to post m and thence by on to switch f instead of direct to switch f 2 but when my receivers are used one plate of each receiver must be in electric connection with that part of the line which extends between the generating secondary coil and some other secondary coil in the line, while the other plate of the receiver may be grounded or may be in electric connection with the line, as described in my Patent No. 240,578, above named; for, as my system of telephony depends wholly upon the electromotive force on the line, and has nothing to do with current strength, one plate of the re ceiver must be connected with a part of the line atahigh electric potential, the other plate being grounded or otherwise arranged so that the difference of potential between the two plates may be sufficient.

One feature ofmy invention consists in the combination of a transmitter and a circuit breaker with the battery and helix of the primary circuit of an inductorium, the secondary of which contains a call-bell, S, or other signaling mechanism, as well as suitabletelephonic instruments, whereby the battery is enabled to be used either for calling or for conversation; and this part of my invention is adapted for use with magneto-receivers m", as well as with my receivers R.

Another feature of my invention consists in the combination of two or more second ary coils with two or more of my receivers R in the manner described, so that one plate of each receiver shall be connected to a point in the line which is separated from the ground by one of the secondary coils or equivalent high resistance, for it will be seen that the potential at any point on the line between the secondary coil at the transmittingstation (by which the current in the line is generated) and the secondary coil at the receiving-station through which the currentmust pass to ground depends (other things being equal) upon the resistance of the latter secondary coil; and as it is essential that the plates of my receiver shall difi'er widely in potential, one of them must be connected to some point of the line between the generating secondary coil and the resistance.

It will be clear that that part of the primary marked a may connect directly with a",instead of through h g, as shown, and also that the details may be otherwise largely varied, as my invention does not relate to the details, .but to the combination of the inductoriums and their transmitters with the circuit-breaker in the primary and signaling and telephone instruments in the secondary circuits of the inductoriums, and the connection of one plate of my receiver with that portion of a grounded line or circuit otherwise closed Whose potential depends upon a resistance in the line.

In Fig. 4 I have illustrated three stations in one line; but it will be seen that all the terminal stations of any line will be substantially as shown in Figs. 3 and 4, and all intermediate stations substantially as shown by the intermediate station in Fig. 4.

By the arrangement of devices shown in the drawings I am enabled to charge the dielectric coating of the plates of the receivers R; but this formed the subject-matter of another application for United States Patent and of my English Patent No. 5,870 of 1882.

What I claim as myinvention is 1. In combination, two or more inductoriums, each having two primary circuits, a transmitter in one primary circuit of each inductorium, a circuit-breaker in the other primary circuit of each inductorium, and signalinstruments and receivers in the line formed by the secondaries of the inductoriums, as set] forth.

2. I11 combination, two or more inductoriums, the secondaries of which form a line grounded at each end, signaling-instruments in that line, and a circuitbreaker in the primary of each inductorium, the operation of the circuit-breaker at either station causing induced currents in the line and operating the signalinginstrument in the line at a distant station, substantially as described.

3. An inductoriurn having in its primary circuit both a transmitter and an apparatus for rapidly making and breaking the circuit, and both a signaling-instrument and a receiver in its secondary circuit, whereby the sudden makes and breaks of the primary circuit induce in the secondary currents sutficient to operate the signaling-instrument, as set forth.

4. In combination, two or more inductoriums, the secondaries of which form a closedline circuit and the primaries of which contain telephonic transmitters, with one or more receivers, each consisting of two plates, one

plate of each receiver being connected to the line at a point between two secondary coils, substantially as described.

AMOS EMERSON DOLBEAR.

Vitnesses:

G. B. 1VIAYNADIER, J. R. Snow. 

